# Copyright (c) 2015 Ansible, Inc.
# All Rights Reserved.

import random
from decimal import Decimal

from django.core.validators import MinValueValidator
from django.db import models, connection
from django.db.models.signals import post_save, post_delete
from django.dispatch import receiver
from django.utils.translation import ugettext_lazy as _
from django.conf import settings
from django.utils.timezone import now, timedelta

from solo.models import SingletonModel

from awx import __version__ as awx_application_version
from awx.api.versioning import reverse
from awx.main.managers import InstanceManager, InstanceGroupManager
from awx.main.fields import JSONField
from awx.main.models.base import BaseModel, HasEditsMixin
from awx.main.models.inventory import InventoryUpdate
from awx.main.models.jobs import Job
from awx.main.models.projects import ProjectUpdate
from awx.main.models.unified_jobs import UnifiedJob
from awx.main.utils import get_cpu_capacity, get_mem_capacity, get_system_task_capacity
from awx.main.models.mixins import RelatedJobsMixin

__all__ = ('Instance', 'InstanceGroup', 'JobOrigin', 'TowerScheduleState',)


class HasPolicyEditsMixin(HasEditsMixin):

    class Meta:
        abstract = True

    def __init__(self, *args, **kwargs):
        r = super(BaseModel, self).__init__(*args, **kwargs)
        self._prior_values_store = self._get_fields_snapshot()
        return r

    def save(self, *args, **kwargs):
        super(BaseModel, self).save(*args, **kwargs)
        self._prior_values_store = self._get_fields_snapshot()

    def has_policy_changes(self):
        if not hasattr(self, 'POLICY_FIELDS'):
            raise RuntimeError('HasPolicyEditsMixin Model needs to set POLICY_FIELDS')
        new_values = self._get_fields_snapshot(fields_set=self.POLICY_FIELDS)
        return self._values_have_edits(new_values)


class Instance(HasPolicyEditsMixin, BaseModel):
    """A model representing an AWX instance running against this database."""
    objects = InstanceManager()

    uuid = models.CharField(max_length=40)
    hostname = models.CharField(max_length=250, unique=True)
    created = models.DateTimeField(auto_now_add=True)
    modified = models.DateTimeField(auto_now=True)
    last_isolated_check = models.DateTimeField(
        null=True,
        editable=False,
    )
    version = models.CharField(max_length=24, blank=True)
    capacity = models.PositiveIntegerField(
        default=100,
        editable=False,
    )
    capacity_adjustment = models.DecimalField(
        default=Decimal(1.0),
        max_digits=3,
        decimal_places=2,
        validators=[MinValueValidator(0)]
    )
    enabled = models.BooleanField(
        default=True
    )
    managed_by_policy = models.BooleanField(
        default=True
    )
    cpu = models.IntegerField(
        default=0,
        editable=False,
    )
    memory = models.BigIntegerField(
        default=0,
        editable=False,
    )
    cpu_capacity = models.IntegerField(
        default=0,
        editable=False,
    )
    mem_capacity = models.IntegerField(
        default=0,
        editable=False,
    )

    class Meta:
        app_label = 'main'

    POLICY_FIELDS = frozenset(('managed_by_policy', 'hostname', 'capacity_adjustment'))

    def get_absolute_url(self, request=None):
        return reverse('api:instance_detail', kwargs={'pk': self.pk}, request=request)

    @property
    def consumed_capacity(self):
        return sum(x.task_impact for x in UnifiedJob.objects.filter(execution_node=self.hostname,
                                                                    status__in=('running', 'waiting')))

    @property
    def remaining_capacity(self):
        return self.capacity - self.consumed_capacity

    @property
    def role(self):
        # NOTE: TODO: Likely to repurpose this once standalone ramparts are a thing
        return "awx"

    @property
    def jobs_running(self):
        return UnifiedJob.objects.filter(execution_node=self.hostname, status__in=('running', 'waiting',)).count()

    @property
    def jobs_total(self):
        return UnifiedJob.objects.filter(execution_node=self.hostname).count()

    def is_lost(self, ref_time=None, isolated=False):
        if ref_time is None:
            ref_time = now()
        grace_period = 120
        if isolated:
            grace_period = settings.AWX_ISOLATED_PERIODIC_CHECK * 2
        return self.modified < ref_time - timedelta(seconds=grace_period)

    def is_controller(self):
        return Instance.objects.filter(rampart_groups__controller__instances=self).exists()

    def is_isolated(self):
        return self.rampart_groups.filter(controller__isnull=False).exists()

    def refresh_capacity(self):
        cpu = get_cpu_capacity()
        mem = get_mem_capacity()
        self.capacity = get_system_task_capacity(self.capacity_adjustment)
        self.cpu = cpu[0]
        self.memory = mem[0]
        self.cpu_capacity = cpu[1]
        self.mem_capacity = mem[1]
        self.version = awx_application_version
        self.save(update_fields=['capacity', 'version', 'modified', 'cpu',
                                 'memory', 'cpu_capacity', 'mem_capacity'])


class InstanceGroup(HasPolicyEditsMixin, BaseModel, RelatedJobsMixin):
    """A model representing a Queue/Group of AWX Instances."""
    objects = InstanceGroupManager()

    name = models.CharField(max_length=250, unique=True)
    created = models.DateTimeField(auto_now_add=True)
    modified = models.DateTimeField(auto_now=True)
    instances = models.ManyToManyField(
        'Instance',
        related_name='rampart_groups',
        editable=False,
        help_text=_('Instances that are members of this InstanceGroup'),
    )
    controller = models.ForeignKey(
        'InstanceGroup',
        related_name='controlled_groups',
        help_text=_('Instance Group to remotely control this group.'),
        editable=False,
        default=None,
        null=True
    )
    policy_instance_percentage = models.IntegerField(
        default=0,
        help_text=_("Percentage of Instances to automatically assign to this group")
    )
    policy_instance_minimum = models.IntegerField(
        default=0,
        help_text=_("Static minimum number of Instances to automatically assign to this group")
    )
    policy_instance_list = JSONField(
        default=[],
        blank=True,
        help_text=_("List of exact-match Instances that will always be automatically assigned to this group")
    )

    POLICY_FIELDS = frozenset((
        'policy_instance_list', 'policy_instance_minimum', 'policy_instance_percentage', 'controller'
    ))

    def get_absolute_url(self, request=None):
        return reverse('api:instance_group_detail', kwargs={'pk': self.pk}, request=request)

    @property
    def capacity(self):
        return sum([inst.capacity for inst in self.instances.all()])

    @property
    def jobs_running(self):
        return UnifiedJob.objects.filter(status__in=('running', 'waiting'),
                                         instance_group=self).count()

    @property
    def jobs_total(self):
        return UnifiedJob.objects.filter(instance_group=self).count()

    '''
    RelatedJobsMixin
    '''
    def _get_related_jobs(self):
        return UnifiedJob.objects.filter(instance_group=self)


    class Meta:
        app_label = 'main'


    def fit_task_to_most_remaining_capacity_instance(self, task):
        instance_most_capacity = None
        for i in self.instances.filter(capacity__gt=0).order_by('hostname'):
            if not i.enabled:
                continue
            if i.remaining_capacity >= task.task_impact and \
                    (instance_most_capacity is None or
                     i.remaining_capacity > instance_most_capacity.remaining_capacity):
                instance_most_capacity = i
        return instance_most_capacity

    def find_largest_idle_instance(self):
        largest_instance = None
        for i in self.instances.filter(capacity__gt=0).order_by('hostname'):
            if i.jobs_running == 0:
                if largest_instance is None:
                    largest_instance = i
                elif i.capacity > largest_instance.capacity:
                    largest_instance = i
        return largest_instance

    def choose_online_controller_node(self):
        return random.choice(list(self.controller
                                      .instances
                                      .filter(capacity__gt=0)
                                      .values_list('hostname', flat=True)))


class TowerScheduleState(SingletonModel):
    schedule_last_run = models.DateTimeField(auto_now_add=True)


class JobOrigin(models.Model):
    """A model representing the relationship between a unified job and
    the instance that was responsible for starting that job.

    It may be possible that a job has no origin (the common reason for this
    being that the job was started on Tower < 2.1 before origins were a thing).
    This is fine, and code should be able to handle it. A job with no origin
    is always assumed to *not* have the current instance as its origin.
    """
    unified_job = models.OneToOneField(UnifiedJob, related_name='job_origin')
    instance = models.ForeignKey(Instance)
    created = models.DateTimeField(auto_now_add=True)
    modified = models.DateTimeField(auto_now=True)

    class Meta:
        app_label = 'main'


def schedule_policy_task():
    from awx.main.tasks import apply_cluster_membership_policies
    connection.on_commit(lambda: apply_cluster_membership_policies.apply_async())


@receiver(post_save, sender=InstanceGroup)
def on_instance_group_saved(sender, instance, created=False, raw=False, **kwargs):
    if created or instance.has_policy_changes():
        schedule_policy_task()


@receiver(post_save, sender=Instance)
def on_instance_saved(sender, instance, created=False, raw=False, **kwargs):
    if created or instance.has_policy_changes():
        schedule_policy_task()


@receiver(post_delete, sender=InstanceGroup)
def on_instance_group_deleted(sender, instance, using, **kwargs):
    schedule_policy_task()


@receiver(post_delete, sender=Instance)
def on_instance_deleted(sender, instance, using, **kwargs):
    schedule_policy_task()


# Unfortunately, the signal can't just be connected against UnifiedJob; it
# turns out that creating a model's subclass doesn't fire the signal for the
# superclass model.
@receiver(post_save, sender=InventoryUpdate)
@receiver(post_save, sender=Job)
@receiver(post_save, sender=ProjectUpdate)
def on_job_create(sender, instance, created=False, raw=False, **kwargs):
    """When a new job is created, save a record of its origin (the machine
    that started the job).
    """
    # Sanity check: We only want to create a JobOrigin record in cases where
    # we are making a new record, and in normal situations.
    #
    # In other situations, we simply do nothing.
    if raw or not created:
        return

    # Create the JobOrigin record, which attaches to the current instance
    # (which started the job).
    job_origin, new = JobOrigin.objects.get_or_create(
        instance=Instance.objects.me(),
        unified_job=instance,
    )
